[PATCH 4/7] Input: cyttsp - Reduce reset pulse timings
From: Linus Walleij <hidden>
Date: 2021-03-30 08:55:22
Subsystem:
cyttsp touchscreen driver, input (keyboard, mouse, joystick, touchscreen) drivers, the rest · Maintainers:
Linus Walleij, Dmitry Torokhov, Linus Torvalds
The data sheet for CY8CTMA340 specifies that the reset pulse shall be at least 1 ms. Specify 1-2 ms with usleep_range() to cut some slack for the scheduler. Curiously the datasheet does not specify how long we have to wait after a hard reset until the chip is up, but I have found a vendor tree (Samsung GT-S7710) that has code for this touch screen and there this is set to 5 ms so I use this with the same 1 ms fuzz. Signed-off-by: Linus Walleij <redacted> --- drivers/input/touchscreen/cyttsp_core.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/input/touchscreen/cyttsp_core.c b/drivers/input/touchscreen/cyttsp_core.c
index 91f8f38b3f06..84f4f1c1a220 100644
--- a/drivers/input/touchscreen/cyttsp_core.c
+++ b/drivers/input/touchscreen/cyttsp_core.c@@ -230,10 +230,16 @@ static int cyttsp_set_sysinfo_regs(struct cyttsp *ts) static void cyttsp_hard_reset(struct cyttsp *ts) { if (ts->reset_gpio) { + /* + * According to the CY8CTMA340 datasheet page 21, the external + * reset pulse width should be >= 1 ms. The datasheet does not + * specify how long we have to wait after reset but a vendor + * tree specifies 5 ms here. + */ gpiod_set_value_cansleep(ts->reset_gpio, 1); - msleep(CY_DELAY_DFLT); + usleep_range(1000, 2000); gpiod_set_value_cansleep(ts->reset_gpio, 0); - msleep(CY_DELAY_DFLT); + usleep_range(5000, 6000); } }
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2.29.2